U.S. Pat. No. 3,745,870 (incorporated by reference) disclosed a new and improved saw chain construction, including novel side cutter and raker teeth. The side cutter teeth could be easily formed and inexpensively manufactured. Flexible cutter elements permitted the teeth to flex laterally under cutting loads, thereby accommodating shocks from binding of the saw chain by forces directed inwardly upon the cutter elements. The improved side cutter tooth of that invention included a cutter element which had a complex curvature. As shown in FIG. 4 of that patent, each element first curved outwardly in a radius indicated by arrow 29. Second, each cutter element curved upwardly in a second radius indicated by arrow 31. Third, each cutter element extended in a final substantially straight course from the second radius 31 upwardly at a constant angle to the tip 32. Due to this final, straight portion, the side cutter element usually bent at the second radius 31 when it experienced inwardly directed forces. These inwardly directed forces reduced the 7.degree. vertical angle of the element by moving the tip inwardly toward the centerline of the kerf. The forces lowered the relative position of the second radius 31 with respect to the first radius 29 and with respect to the body of the tooth, forming a crimp in the cutter element. Within a short time, the tooth broke at the crimp.
Having about three times better performance and longer life than earlier developed teeth, the side cutter tooth of U.S. Pat. No. 4,426,900 (incorporated by reference) had a cutter element that included a continuously curved portion which was attached to the body of the side cutter tooth and which extended outwardly in a half-space adjacent the body. The continuous curve of the cutter element caused the cutter element to bend substantially at the intersection of the body and the cutter element when the cutter element was exposed to inwardly directed forces (which tended to flatten the curved portion from the half-space into the plane of the body). In this way, crimping of the cutter element was substantially reduced. The intersection between the body and the cutter element provided greater resistance to deformation and, therefore, ensured that the tooth would perform better and longer than elements having a complex curvature, such as those in U.S. Pat. No. 3,745,870. The cutter element, however, still flexed laterally under cutting loads to reduce binding of the saw chain and to promote better performance. Thus, the improved side cutter tooth retained the advantages disclosed in U.S. Pat. No. 3,745,870 with increased cutting life. Breakage of these teeth, however, often was unacceptably high, especially when cutting soft woods, because the teeth could deflect outwardly when a load was directed downwardly on the element when attempting to pry the saw from a bind.